Diagnosis of invasive aspergillosis using bronchoalveolar lavage in haematology patients: influence of bronchoalveolar lavage human DNA content on real-time PCR performance

In order to improve invasive pulmonary aspergillosis (IPA) diagnosis, a real-time polymerase chain reaction (PCR) assay detecting Aspergillus spp. was developed. Its detection limit reached 2-20 conidia. The retrospective evaluation on 64 bronchoalveolar lavage (BAL) fluids from 57 patients at risk for IPA, including 20 probable and five proven IPA patients, revealed a 88% or 38% sensitivity in direct examination (DE)/culture-positive or culture-negative BAL, respectively, whereas galactomannan (GM) sensitivity reached 88% or 58%, respectively. Influence on the Aspergillus-PCR yield of BAL fluid volume, cellular count and DNA content (evaluated by human beta-globin quantification) was assessed. Significantly higher beta-globin levels were detected in Aspergillus PCR-positive (median 5,112 pg/mu l) than negative (median 1,332 pg/mu l) BAL fluids, suggesting that the beta-globin level could reflect BAL yields and DNA extraction. Using beta-globin for the interpretation of fungal PCR could improve the negative predictive value of this test.